Evaluation of serum amino acid profile in patients with advanced Parkinson's disease.

Objectives: Levodopa-induced dyskinesia (LID) complicate treatment of advanced Parkinson's disease (PD). Branched-chain amino acids (BCAA) compete with levodopa in crossing brain-blood barrier, modulating the availability of dopamine in brain. Serotoninergic and glutamatergic transmission are also implicated in pathophysiology of LID. We hypothesize that differences in serum concentrations of BCAA[1], glutamate[2], and tryptophan[3] may be related with LID development. The purpose of this study was to assess the amino acids serum profile in PD patients with dyskinesia (LID+) and without dyskinesia (LID-).